(CNN) -- NASA lost regular communication with the International Space Station on Tuesday and has since established only limited connections.
The space agency said it was doing a routine update of computer software when communications were lost, leaving the craft able to communicate only every 90 minutes when it passes over ground stations in Russia.
"This is the same way they used to do it in the 1960s, with Gemini and Apollo," NASA spokesman Josh Byerly said. "The crew is working on this, and they'll get it back up and running."
The station, which is carrying one American astronaut and two Russian cosmonauts, does not appear to be in danger.
"It's not a panicked mood that takes over mission control," Byerly said. "Anybody's who's been here has seen that."
Aboard the station, Commander Kevin Ford told mission control during a pass over a Russian ground station that the craft is "still flying straight" and that "everybody's in good shape."
The loss in communications is not considered unprecedented, though it is thought to be a cause for concern, officials said.
The station is the product of a partnership among 16 nations and carries six laboratories for space research.